Thread cutting chaser



April 17, 1934. A. F. BREITENSTEIN THREAD CUTTING CHASER Filed NOV. 9,. 1932 HEL /x ANGLI Patented Apr. 17, 1934 THREAD CUTTING CHASER Albert F. Brcitenstein, New Haven, Conn., as-

signer to The Geometric Tool Company, New Haven, Conn., a corporation Application November 9, 193.2, Serial No. 641,846

1 Claim.

This invention relates to an improvement in thread-cutting chasers of the so-called circular type, i. e., chasers of substantially-cylindrical forni and haviner thread-cutting teeth formed upon their peripheries. Circular Chasers as at present in use fall into two distinct classes, narnely, those having truly-annular threadcutting teeth upon their peripheries, and those having helicaliy-inclined thread-cutting teeth thereon.

My invention relates to the latter Class of circular chasers and has for one of its main objects the provision of a circular chaser of the helical-tooth type whichdespite repeated grindings of its cutting-face, Will have its Cuttingteeth located at a substantially-constant distance from its forward face.

A further object of my present invention is to provide a circular Chaser of the type referred to in which the throat or chantier-form will remain substantially the saine, despite repeated grindings of the cutting-face.

@ther objects will he apparent from the following, taken in conjunction with the accompanying drawing.

With the foregoing and other objects in View as will appear from the following, my invention consists in a thread-cutting Chaser of substantially-cyiindrical forni having helically-inclined thread-cutting teeth, together with certain features and configurations as will be hereinafter iore fully set forth.

in the accompanying drawing:

l is a perspective View of one forni which a thread-cutting Chaser constructed in accordance with rny invention may assume;

Fig. 2 is a similar View, but Viewing the Chaser from a different angle;

Fig. 3 is a View of the Chaser in front elevation;

Fig. 4 is a View thereof in side elevation, looking in the direction of the arrow 4 of Fig. 3;

Fig. 5 is a similar View', but looking in the direction of the arrow 5 of Fig. 3;

Fig. 6 is a View of the Chaser in edge elevation, looking in the direction of the arrow 6 of Fig. 3;

Fig. 'l is a transverse sectional view, taken on the line 7-7 of Fig. 3; and

Fig. 8 is a transverse sectional View, taken on the line 8-8 of Fig. 3.

The particular chaser herein chosen for the illustration of my invention has a body 10 of Substantially-cylindrical exterior form, as shown, and has its periphery formed with a series of grooves 11 which are helically inclined from front (C1. lil-103) to rear and result in the formation of a similarlyinclined series of thread-cutting teeth 12. The said teeth 12 are interrupted by a notch 13 extending froin front to rear of the body with a slight outward slope, and resulting in the forrnation of a cutting-face 11i which, as will hereinafter appear, may he repe .tedly ground back as required to keep the Chaser in sharpened condition.

The particular Chaser illustrated in the aocornpanying drawing is provided with an axial bore 15 having formed therein an annular series of serrations 15 by means of which it may be properly orientated and anchored to a suitable stud or post, not shown, and forming a feature of a die-head or other thread-cutting device.

The rear face 1'? of the chaser preferably extends, as shown, at a right angle to the axis of the body 10, .vhile the front face 18 is helically inclined from front to rear at an angle corresponding to the helix angle of the thread-cutting teeth 12 before referred to. It will be appreciated in this connection that the cross-sectional form, as well as the helix angle, of the threadcutting teeth l2 will vary to different re- 8@ quirernents in threading practice, though it is intended that the front to rear inclination of the front face 18, just referred to, shall substantially correspond to the helix angle of the particular thread-cutting teeth formed upon the Chaser. The front face 1S of the Chaser is also preferably so shaped that despite its helical slope from front to rear, it will extend radially at all points at substantially a right angle to the axis of the Chaser, as will clearly appear from Figs. 7 and 8. 90

The forward outer edge or corner of the Chaser is chainfered as at 19, which chainfer slopes with respect to the axis of the cody and joins the forward face 18 at a point below the root of the thread-cutting teeth l2 to facilitate the starting 95 of a threading operation in accordance with usual practice. In addition to sloping with respect to the axis of the body-member, the charnfer is also ground at a helical angle from front to rear substantially conforming to the helix angle of the thread-cutting teeth 12.

Preferably and as shown, the helix angle of the chainfer 19 slightly exceeds the helix angle of the thread-cutting teeth l2, as will be observed from the extension lines marked upon Fig. 5. This feature will also be apparent from other iigures of the drawing. In Figs. 7 and 8, for instance, it Will be obvious that the Charnfer extends progressively more deeply into the thread-cutting teeth 12 as the distance increases from the cutting-face 14. This slight increase in helical angle of the chaser is designed to provide clearance to facilitate the cutting action of the front portion of the chaser.

By so inclining the front face 18 of the body 10 from front to rear as shown, to substantially conform in helix angle to the helix angle of the thread-cutting teeth l2, any given one of the latter will be found to be located at substantially the same distance from the said front face 18. The feature just referred to will be made clear by reference to Figs. '7 and 8, in Which it will be noted, by comparing the distance A marked thereon, that in each instance they correspond.

As the chaser is subjected to continued use, it will be desirable to repeatedly grind the cuttingface 14 and in time it may be that the said cuttingface Will be ground back, for instance, as far as is indicated by the broken lines 14a in Fig. 3. Despite this grinding back, the character of the cutting-face 14 presented to the work will not materially change, Whereas in prior types of circular chasers having helically-inclined threadcutting teeth, progressive grinding operations will inevitably alter the distance between the front face of the chaser and the cutting-teeth, and thus present a cutting-face of progressively changing character` as the cutting-face is ground back for sharpening purposes.

My improved chaser, if initially designed to cut threads upon a shouldered object up to Within a given distance of the shoulder thereon, may have its cutting-face 14 repeatedly ground even to the extent indicated at 14a in Fig. 3, Without materially altering the character of the thread which the chaser Will produce upon the Work adjacent such a shoulder.

Viewed from another angle, my improved chaser may be said to have capacity for maintaining the substantial sameness of its chamfer characteristics 19, despite the repeated grinding back of its cutting-face 14.

Thus, instead of constructing a circular chaser which has the same depth from front to rear at any given place adjacent its periphery, my improved chaser may be said to progressively decrease in depth from front to rear in substantial conformity with the helix angle of the threadcutting teeth thereof.

It will be understood by those skilled in the art that my invention may assume varied physical forms without departing from my inventive concept, and I, therefore, do not limit my invention to the specic embodiment herein chosen for illustration, but only as indicated in the appended claim.

I claim:

A thread-cutting chaser of substantially-cylindrical form and having its periphery helically grooved to form helically-inclined thread-cutting teeth thereon, and having its front face helically inclined from front to rear in the same direction and at substantially the same helix angle as the said helically-inclined thread-cutting teeth; the said chaser having a cutting face extending substantially-parallel to its axis and also having its forward outer edge chamfered along an inclined helical path from front to rear at a helical angle exceeding the helix angle of both the said thread-cutting teeth and the said helically-inclined front face; the rear edge of the said chamfer being of progressively-lessening height above the bottom of the adjacent helical groove.

ALBERT F. BREITENSTEIN. 

